The present application relates to microelectronic assemblies including inductors, and to components and methods useful in making such assemblies.
Semiconductor chips or dies commonly are provided in packages that facilitate handling of the chip during manufacture and mounting of the chip on an external substrate such as a circuit board or other circuit panel. For example, certain packaged semiconductor chips sold under the registered trademark μBGA® by Tessera, Inc., assignee of the present application, incorporate a dielectric element having terminals. The terminals are connected to contacts on the die itself. In particularly preferred arrangements, the connections between the terminals and the die are formed by flexible leads and the dielectric element, its mounting to the die or both are arranged so that the terminals remain moveable with respect to the chip. For example, where the dielectric element overlies a surface of the chip, a layer of a compliant material may be provided between the dielectric element and the chip. The packaged chip can be mounted to a circuit board or other underlying circuit panel by soldering or otherwise bonding the terminals on the dielectric element to contact pads on the circuit board. Because the terminals on the dielectric element can move relative to the chip, the assembly can compensate for differential thermal expansion and contraction of the chip and the circuit board during thermal cycling in service, in storage and during manufacturing processes.
Assemblies of this type are described, for example, in U.S. Pat. Nos. 5,148,265; 5,148,266; and 5,679,977. In certain embodiments, the leads can be formed partially or wholly as elongated metallic strips extending from the terminals along the dielectric element. These strips can be connected to the contacts on the chip by wire bonds, so that the wire bonds and strips cooperatively constitute composite leads. In other embodiments, the strips themselves can be connected directly to the terminals. Certain methods of forming strip-like leads and connecting numerous strip-like leads to numerous contacts on a die are described in U.S. Pat. Nos. 6,054,756; 5,915,752; 5,787,581; 5,536,909; 5,390,844; 5,491,302; 5,821,609; and 6,081,035, the disclosures of which are incorporated by reference herein.
The aforementioned structures, in their preferred embodiments, provide packaged chips with numerous advantageous including the aforementioned ability to compensate for differential thermal expansion and hence high reliability; compatibility with surface-mounting techniques for assembling components to a circuit board and the ability to accommodate numerous connections to the chip in a compact assembly. Some of these packages occupy an area of the circuit board just slightly larger than the area of the chip itself. Certain preferred packages of this type provide short, strip-like leads which minimize self-inductance in the leads and hence provide good high-frequency signal propagation. Moreover, certain packages according to this design can provide good heat dissipation from the chip. These packages have been widely adopted for semiconductor chips in numerous applications.
Some circuits incorporating semiconductor chips also include so-called “passive” electronic components, such as inductors, resistors and capacitors. While some passive components can be incorporated in the semiconductor chip itself, this adds to the size and cost of the chip. Moreover, it is difficult to provide substantial inductance in chips fabricated using conventional chip-making techniques. It has been proposed to provide passive components in a packaged module with the chip itself, so as to provide a relatively compact unit, which can be handled and mounted in much the same way as a packaged semiconductor chip. Merely by way of example, certain modules incorporating inductors are shown in U.S. Pat. Nos. 5,973,391; 6,218,729; 6,310,386; 6,362,525; and 6,377,464; and Japanese Publication JP 05-04762 published Feb. 26, 1993. However, despite these efforts in the art, there have been needs for improvements in inductors suitable for use in microelectronic packages and in microelectronic packages incorporating inductors. There have been corresponding needs for improvements in the components and methods used to form such packages and inductors themselves.